1. Field of the Invention
The invention relates to a control apparatus and control method for an internal combustion engine that uses low volatile fuel such as alcohol fuel, for example.
2. Description of the Related Art
Japanese Patent Application Publication No. 2007-224878 (JP-A-2007-224878) describes a control apparatus for an internal combustion engine that uses alcohol fuel. Alcohol fuel does not easily vaporize particularly at low temperatures, so a vaporizing chamber to vaporize the fuel at startup is provided in the internal combustion engine of the related art. This vaporizing chamber has a closed structure in which it is cut off from the outside, and is connected to an intake passage via a throttled passage. Also, a startup fuel injection valve that injects fuel into the vaporizing chamber, and a heater for heating the injected fuel are both provided in the vaporizing chamber.
At startup of the internal combustion engine, the heater is first activated when a start signal is output to the internal combustion engine. Then when an appropriate amount of time has passed, fuel is injected into the vaporizing chamber from the startup fuel injection valve. When fuel is injected, the pressure in the vaporizing chamber becomes reduced due to the effect of intake vacuum produced by cranking. As a result, the injected fuel vaporizes from the heat of the heater in the reduced-pressure vaporizing chamber, and is supplied to the cylinders via the intake passage. In this way, the related art ensures startability during a cold-start, for example, by vaporizing the fuel in the vaporizing chamber at startup.
Incidentally, with the related art described above, vaporized fuel is produced by injecting fuel into the vaporizing chamber after activating the heater at startup. However, in this case, after the start signal is output to the internal combustion engine, the temperature of the heater rises, the injected fuel is heated, and the pressure in the vaporizing chamber is reduced, and as a result, vaporized fuel is produced. Therefore, with the related art, it takes time to produce vaporized fuel at startup, so the amount of vaporized fuel that is supplied may be insufficient, and as a result, startability and emissions characteristics may be poor.